Method of producing elemental sulphur



Aug. 19, 1930.

R. c. BENNER `METHOD OF PRODUCING ELEMENTAL SULPHUR Filed Jah. 21, 1927 E .58 RUSS Patented Aug, l, 193@ irang srs rATENTol-FICE RAYMOND C. 'BENNER, OF NIAGARA EaiLS,` NEW YOBK, .ASSIGNOR TO GENERAL CHEMICAL COMPANY, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK IHETHODOF PRODUCING ELEMENTAL SULPHUR Application led January 21 1927. Serial No; 182,572.

' rI'his invention relates to a method of producing elemental sulphur from gases containing sulphur compounds such as sulphur dioxide, hydrogen sulfide, carbonyl. sulfide, etc., and particularly to a method of producing elemental sulphur by the reduction of sulphur dioxide 'as it occurs in gases from roasting or smelting furnaces or the like by means of solid or liquid carbonaceous fuel.

In the processes heretofore known for the production of elemental sulphur from sul.- phur dioxide by the reduction of the oxide by carbonaceous fuel, especially solid fuel, great difliculties have been experienced in obtaining a product which is not contaminated with soot or solid carbonaceous particles and which is of such purity that it may be used for the purposes for Which-brimstone is ordinarily employed. Furthermore, not only does the presence of soot or solid carbonaceous particles contaminate the product ,but it renders the operation of condensing and collecting the elemental sulphur exceedingly diiiicult. Mechanical dust collectors have not-proven satisfactory as a means for removing the soot and carbonaceous matter and obviously a strong .oxidizing atmosphere cannot be employed to burn the soot sincev such a condition would cause an oxidation of the sulphur. The general procedure, therefore, has been to employ a carbonaceous fuel 'yielding as little soot as possible and to distill the resulting sulphur product.

It is the object of my invention to provide a process for the rapid reduction of sulphur dioxide either in the pure state or in gas mixtures by means of solid or liquid 'carbonaceous fuels and the recovery of elemental sulphur therefrom whereby substantially all the 40 sulphur introduced into the 'system is re- -covered in the elemental form and the gas leaving the system contains but small amounts of gaseous sulphur compounds which would reduce the eiciency of the process and create a nuisance. It is a further object of my invention to provide a process wherein reducing fuel normally yielding considerable soot and hydrocarbons may be employed and whereby substantially all the soot produced in the reduction of the sulpuur dioxide is eliminated from the system and the elemental sulphur produced may be recovered in a substantially pure state suitable for purposes ordinarily requiring brimstone.

Broadly, my invention consists in passing' sulphur dioxide gas through incandescent carbonaceous reducin materials, or reducing A sulphur dioxide wit liquid carbonaceous fuels, adjusting the composition of the resulting gas by the addition of an oxidizing gas such as sulphur dioxide gas to provide approximately reacting proportions of reducing and reducible gases, burning such mixture'in a suitable combustion chamber '65 maintained at a temperature of 7501000 (J. or above, and in the presence of a porous refractory material whereby a preferential oxidation of the soot or carbon particles withl sulphur dioxide and carbon dioxide is accomplished without oxidation of the elemental sulphur formed, cooling the gas mixture,` and subsequently contacting the remaining gaseous products with a suitable catalyst capable of causing the interaction of any re- .75 i

maining reducing and reducible gases to produce elemental sulphur.

In the accompanying drawing Figs. 1 and 2 illustrate diagrammatically two preferred systems for carrying out my novel process. B0 Fig. 1 illustrates a system especially adapted to produce elemental sulphur when the reducing fuel contains little hydrogen eithera as free hydrogen or asv combined hydrogen in the form of hydrocarbons, water vapor, etc., While Fig. 2 illustrates a system especially adapted to produce elemental sulphur whenV the gaseous products from the reduction contain substantial amounts of hydrogen sulfide. Fig. 3 represents a sectional ele- 90 vation of the combustion chamber. I

The gas containing sulphur dioxide with oriwithout other gaseous sulphur compounds such as may occur in the exit of smelters or as obtained directly by the roastin of sulfide ores is first caused to react with solid or liquid carbonaceous fuels. If the as contains but a small amount of sulphurV ioxide, this sulphur dioxide may be concentrated by any of the well-known methods such as liquefaction and vaporization, absorption in oil or water, or in solid absorbents such as alumina or dehydrated bauxite, with subsequent liberation by heat, etc. According to my preferred method the sulphur dioxide gas containing for example 7% sulphur dioxide, or concentrated as desired, is introduced into the reduction chamber l and passes upwardly through a descending bed of solid carbonaceous` fuel which is maintained in ainincandesc'ent state.' The solid fuel may be either bituminous or anthracite coal, lignite, or coke, etc.. my process being especially adapted to utilize cheap carbonaeeous fuel high in ash and sulphur and yielding considerable sootand volatile hydrocarbons. The fuel is consumed by the free oxygen present and by the sulphur dioxide forming carbon dioxide and sulphur, the carbon dioxide being subsequently reduced by more carbon to form carbon monoxide. The heat vevolved b v these reactions serves to drive olfthe volatile hyl droearbons which are present in the fuel, and

these hydrocarbons in the reducing atmosphere break down to yield carbon, in the form of soot, and hydrogen.

The gas mixture leaving the reduction chamber l will usually contain considerable amounts of carbon, even as high as 23% of the total carbon introduced into the system, as fine particles in the form of soot. 'l`hc mixture also contains an excess of reducing gases such as carbon monoxide. hydrogen, hydrocarbons, hydrogen sulfide, ctc., as well as a small amount of unreduced sulphur dioxide, some carbonyl sulfide and consider.- able sulphur vapor. If this soot is permitted to remain in the system. it will seriously interfere with the subsequent catalytic reaction of the reducing gases with additional sulphur dioxide` and with the condensation and collection of the elemental sulphur, and eventually clog-the system as well as contaminate the tinal product. I have discovered that this carbon may be eliminated by .preferential oxidation thereof under such conditions that the elemental sulphur piesent will not be affected but the carbon will be completely consumed.

The hot gas mixture from the reduction chamber, when containing an excess vof re ducing gases, is mixed with an oxidizing gas` preferably sulphur dioxide containing gas by-passed around the reduction chamber. The amount of such sulphur dioxide will be regulated by the valve S) so that there will be approximately interactingr proportions of reducing gas and redueible gas or a` slight excess of reducing gas. The mixing of the gases will preferably be done as soon-as possible after the hot gas leaves the reduction chamber and before it cools in order to prevent the formation of additional soot by the ing to the equation 1 2CD-CO2 C.

'hen the gas mixture from the reduction chamber already contains approximately interacting proportions of reducing and'reducible gases of course no additional sulphur dioxide is introduced. The mixed gases are conducted to'a suitable combustion chamber Q where the interaction of the reducing and rcducible gases takes place with the evolution of a large amount of heat. The gases enter the combustion chamber through the inlet l2 and pass upwardly. The chamber is preferably provided with suitable checkcrworlt ll with which the.gases lirst contact and which serves to thoroughly mix the gases and aid the combustion, and with porous refraetory material 13 positioned above the checkerwork and transversely' of the gas streani through which the soot-contaminated gas` subsequently filters. By the term filter l do not mean that the refractory material is necessarily of such physical form as to continuously mechanically hold all the'solid matter, but rather of such a nature that the solid particles impinging thereon by the baffling effect are momentarily held until such particles are consumed b v the sulphur dioxide or carbon dioxide in the gas stream.

vhatever free oxygen is present in the hy-passed sulphur dioxide gas is first utilized in burning carbon monoxide to carbon dioxide. The reduction of the sulphur dioxide by the several reducing gases takes place according to the following typical equations:

A portion of the soot is therefore burned aecording to Equation (5). but since the proportion of sulphur dioxide limited, its concentration becomes small and the reaction is slow and incomplete. I have found` however. that by maintaining the temperature at 7500 C. or above, and preferably at about SOG-900 C., I am able to completely eonsume the soot in the presence of suitable refractory catalytic material by preferential oxidation thereof with carbon dioxide, which is normally present in the gas mixture at this point to the extent of about 124076. The reaction occurs according to the e'piation I have found that the natural mineral bauxite serves excellently as a porous refractory material to catalyze the reaction. Other refractory material may be employed such as aluminum oxide or broken lire brick, etc. In decomposition of carbon monoxide accordfact. I have found that if the gases are permitted' to contact for a sulticiently long time with the incandescent checkerwork of fire brick and at temperatures of about 900--1000 C.. the layer of porous refractory inateiial may be omitted. llowever. I prefer to eniploy the porous "filteriug material to iiisure the .complete removal ot the soot and to permit lower temperatures ot operation and a smaller combustion chamber. lu normal operation the required temperature is readily maintained by the interaction of the reducing and reducible gases.

In this` inanuer the soot and earbonaceous pai'ticles are .filtered" are separated`froin the gas mixture and are preferentiallv oxidized by the carbon dioxide while tlie elcineiital sulphur remains unoxidized and the gas mixture leaving the combustion chamber through the outlet 14 contains practically no soot or carbonaceous particles which would contaminate the sulphur. The gas mixture trom the combustion chamber also contains a small amount o'f reducing gases such as carbon monoxide. hydrogen sulfide, etc.. and a little sulphur dioxide which have not reacted with the reducing gases because of the displacement of the equilibrium ot the reaction at the high temperature employed. Accordingly. -the, gas mixture is cooled by a suitable heat interchange device 3, as for example a suitable type of waste heat boiler. and the gas mixture contacted with a suitable catalyst to complete the interaction of the sulphur dioxide with the reducing gases.

Referring particularly now to Fig. l, when there is only a small amount ot hydrogen sulfide present in the gas mixture troni the combustion chamber, which will be the case when little hydrogen is introduced into the system. I prefer to maintain a. temperature in the catalyst chamber 1 as low as possible without risking the danger ot' clogging the catalyst with retained sulphur. For normal operation I have found that. a temperature of QSO-350 C. is satisfactory. Suitable catalytic materials which may be employed in the chamber are aluminum oxide,` :terric oxide, pyrites oinder, titanium oxide, bauxite, calcium sulfate, calcium sulfide, etc. The gases leaving the catalyst chamber 4, containing substantially all the sulphur in the elemental form and free from soot, are conducted to a cooler 5 where they are cooled to 120--1500 C., and thence to a. sulphur collector 6 Where the condensed sulphur is separated out and collected in a substantially pui-e state. K

l'lowever, when employing the cheaper reducing fuels. containing substantial amounts ot hydrocarbons. such bituminous coal,

lignite, etc.. which normally yield considerable soot. and tor the utilization ot which our .process` is particularly applicable, the gas sulfide produced from the hydrogen present in the system and which has not interacted with the sulphur dioxide present because of the reverse reaction which occurs readily at the high temperatures and in the presence of sulphur vapor. Iny order to provide for the complete utilization of' this hydrogen sulfide l preferably cool the gas mixture from the. combustion chamber to a temperature of about 120-200" C. in the cooler 3. At this temperature a major portion of the elemental sulphur produced in the combustion chamber is condensed and separates out. The gases may then, if desired. be passed through a suitable sulphur collector 7 (Fig. 2) to remove substantially all' ot' the condense-d sulphur from the gas stream. or they may be passed directly to the catalyst.. chamber 8 without such sulphur removal. In either method the gases containing h vdrogen sulfide and sulphur dioxide are caused to enter the catalyst chamber 8 at about 120-200o C., and preferably at about 120-1500 C. It the gases are normally belowr this temperature as may be the case when the gas is passed through a sulphur collector, a heater 10 is provided to maintain the requisite temperature. It there is an insulticient amount of oxidizing gas present. i..e.

lsulphur dioxide. oxygen, or air, to completely oxidize the hydrogen sulfide. more will be added to provide at least interacting proportions. The mixture thus prepared 1s contacted with-a suitable catalyst While maintaining the temperature below that at which sulphur has an appreciable vapor pressure, i. e. below about 200 C. The hydrogen sulfide and sulphur dioxide react completely under these conditions of operation to yield elemental sulphur and water according to solutions of the heavy metals. The sulphur produced by the interaction and thatpresent in the gas mixture coming to the catalyst will condense and a major portion run out. lVlien employing activating bauxite. any retained sulphur may be removed atpintervals by the application of heat, whenever the activity of the catalyst becomes substantially decreased. rihe gases leL ving thecataiyst chamber S will be substantiaiiy free from all suiohur cenipounds and may be discharged to the atmosphere.

Vrhile I have referred part-iculariy to the use of soiid carbonaceous fuels for thc reduction of the sulphur dioxide, liquid fuels may also be employed. Various other changes may be made in the manneroi" applying my invention. and Ido not wish to limit. the scope thereof except as deined in the appended claims.

I claim: v

l. In the process of producing elemental sulphur from sulphur dioxide the steps of reducing sulphur dioxide With carbonaceous fuel to produce a gas mixture containing elemental sulphur, regulating the composition of the gas mixture to provide approximately interacting proportions of reducing and reducible gases and substantial amounts of carbon dioxide, and preferentially oxidizing any solid carbonaceous particles present While avoiding the oxidation of the elemental sulphur.

2. In the process of producing elemental sulphur from sulphur dioxide the steps of contacting a gas mixture from a reducing operation containing elemental sulphur, solid carbonaceous particles, and substantial amounts of carbon dioxide with refractory material While maintaining a temperature of 750 C. or above whereby the solid carbonaceous articles are preferentially oxidized and t e elemental sulphur remains unchan ed.

3. n the process of producing elemental sulphur from sulphur dioxide the steps of contacting a gas mixture from a reducing operation containing elemental sulphur, solid carbonaceous particles, and substantial amounts of carbon dioxide with bauxite While maintaining a temperature of 750 C. or above whereby the solid carbonaceous particles are preferentially oxidized and the elemental sulphur remains unchanged.

4. In the process of producing elemental sulphur from sulphur dioxide, the steps of contactingsulphur dioxide gas With carbonaceous fuel, adding'an oxidizing gas containing sulphur dioxide to provide approximately reacting proportions of reducing and reducible gases, and contacting said mixed gases with refractory material While maintaining a temperature of 750 C, or above, whereby any solid carbonaceous particles in the gas mixture are burned.

5. In the process of producing elemental sulphur from sulphur dioxide, the steps of contacting sulphur dioxide gas with carbonaceous fuel, addingl an oxidizing gas containing sulphur dioxide to provide approximately reacting proportions of reducing and reducible gases, the amount of reducing gas being agrarias in small excess, and contacting said mixed gases with refractory material while maintaining a temperature of 750 C. or acove, whereby any solid carbonaceous particles in the gas mixture are burned.

.0. In the process of producing elemental sulphur from sulphur dioxide, the steps of contacting sulphur dioxide gas with carbonaccous fuel, adding an oxidizing gas containing sulphur dioxide to provide approximately reacting proportions of reducing and reducible gases, and contacting said mixed gases f with bauxite While maintaining a temperature of 750 C. or above, whereby any solid carbonaceous particles in the gas mixture are burned.

7. In the process of producing elemental sulphur from sulphur dioxide, the steps of contactingT sulphur dioxide gas With carbonaceous fuel. adding an oxidizing gas containing sulphur dioxide to provide approximately reacting proportions of reducing and reducible gases, the amount of reducing gas being in small excess. and contacting said mixed `gases with bauxite while maintaining a temperature of 750 C. or above, whereby any solid carbonaceous particles in the gas mixture are burned.

8. The process of producing elemental sulphur which comprises the steps of contacting sulphur dioxide with incandescent carbonaceous fuel. regulating the composition of the gaseous product to provide approximately reacting proportions of reducing and reducible gases. maintaining the temperature sufficiently high to burn any solid carbonaceous matter present with sulphur dioxide or carbon dioxide, cooling said gas mixture, contacting said gas mixture with a suitable catalyst to aid the interaction ofthe reducing and reducible gases and recovering the elemental sulphur produced.

9. The process of producing elemental sulphur which comprises the steps of contacting sulphur dioxide with incandescent carbonaceous fuel, regulating the composition of the gaseous product to provide approximately reacting proportions of reducing and reducible gases, contacting the resulting gas mixture with refractory material While maintaining a temperature of 7 50 C. or above, whereby any solid carbonaceous matter present will be burned` coolingsaid gas mixture, contacting said gas mixture with a suitable catalyst to aid the interaction ofthe reducing and reducible gases and collecting the elemental sulphur.

10 The process of producing elemental sulphur which comprises the steps of contacting sulphur dioxide with incandescent carbonaceous fuel, adding sulphur dioxide to the gaseous product to provide approximate- 1y reacting proportions of reducing and reducible gases, sald reducing gasbeing 1n iso temperature of 750 C. or above, whereby any solid carbonaceous mattei' present will be 1burned, cooling said gas mixture, contacting said gas mixture with a suitable catalyst to aid the interaction of the reducing and re,- ducible gases and collecting the elemental sulphur.

11. The process of producing elemental sulphur which comprises the steps of contacting sulphur dioxide with carbonaceous fuel, regulating the composition of the resulting gas mixture to provide approximately interacting proportions of reducing and reducible gases and substantial amounts of carbon dioxide, preferentially oxidizing any solid carbonaceous particles present while avoiding the oxidation of the elemental sulphur, cooling the resulting gas mixture to condense and separate out the elemental sulphur, and contacting the remaining gas with 'a catalyst capable of causing the interaction of 'hydrogen sulfide and an oxidizing gas at a. temperature below that at which sulphur has an appreciable vapor pressure.

1&2. The process of producing elemental sulphur which comprises the steps of contacting sulphur dioxide, with carbonaceous fuel, regulating lthe composition of the resulting gas mixture to provide approximately `interacting proportions of reducing and reducihle gases and substantial amounts of carbon dioxide, preferentially oxidizing any solid carbonaceous.particles present while avoiding the oxidation of the elemental sulphur, cooling the resulting gas mixture to condense and separate out. the elemental sulphur, and contacting the remaining gas with activated bauxite below Q00O C.

13. The process of producing elemental sulphur' which comprises the steps of contacting sulphur dioxide with incandescent carhonaceous fuel, regulating the composition of the gaseous product to provide approximately interacting proportions of reducing and reducihle gases, contacting the resulting gas mixture with refractory material while maintaining a temperature of 750 C. or above. whereby any solid carbonaceous matter present will be burned` cooling said gas mixture to condense the elemental sulphur, contacting the remaining gas with a suitable catalyst capable of causing the interaction of hydrogen sulfide and an oxidizing gas below 200 C., and collecting the elemental sulphur.

14. The process of producing elemental sulphur which comprises the steps of contacting sulphur dioxide with incandescent carbonaceous fuel. adding sulphur dioxide to the gaseous product to provide approximately interacting proportions of reducing and reducible gases. contacting the resulting gas mixture with bauxite while maintaining a temperature of T500 C. or above` \\'hereb any solid carbonaceous matter present -will be burned. cooling said gas mixture to condense the elemental sulphur, contacting the remaining gas with activated bauxite below 2000 C., and collecting the'elemental sulphur.

15. 1n the process of producing elemental sulphur from sulphurdioxide, the steps of contacting sulphur dioxide gas with carbonaceous 't'uel to produce a gas mixture containing elemental sulphur, solid carbonaceous particles, carbon monoxide, and carbon dioxide, adding an oxidizing gas containing sulphur dioxide to the gaseous products of the first mentioned step before any substantial cooling of the said gaseous products has taken place whereby the formation ofsoot by decomposition of carbon monoxide is avoided, and then contacting the gas with refractory material while maintaining a temperature of 750 C. or above whereby the solid carbonaceous particles are preferentially oxidized .and the elemental sulphur remains unchanged.

16. In the process of producing elemental sulphur from sulphur dioxide, the steps of contacting sulphur dioxide gas with carbonaceous fuel under conditions as to produce a gas mixture containing elemental sulphur in comparatively large, recoverable quantities, carbon monoxide, and a con'iparatively small amount of carbonyl sultide, and then adding an oxidizing gas containing sulphur dioxide to the gas mixture of the first mentioned step lefore any substantial cooling of the said gas mixture has taken place, whereby the formation of soot by decomposition of carbon in onoxide is avoided. l

In testimony whereof` l affix my signature.

' RAYMOND C. BENNER. 

